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Abstract:

Power is provided to one or more devices in a system that includes a
hierarchical power smoothing environment having multiple tiers. In
response to a peak in power usage by the one or more devices, power is
provided from a first power smoothing component in a first tier of the
multiple tiers. Additionally, power is provided to the one or more
devices from power smoothing components in each of other tiers of the
multiple tiers if the power smoothing component in a next lower tier of
the multiple tiers is unable to provide sufficient power for the peak in
power usage. If the power smoothing components in the multiple tiers are
unable to provide sufficient power for the peak in power usage, then
performance of at least one of the one or more devices is reduced in
response to the peak in power usage.

Claims:

1. A method in a system, the method comprising: providing, from a first
power smoothing component in a first tier of a hierarchical power
smoothing environment having multiple tiers, power to one or more devices
in the system in response to a peak in power usage by the one or more
devices; providing, from a second power smoothing component in a second
tier of the multiple tiers of the hierarchical power smoothing
environment, power to the one or more devices in response to the peak in
power usage if the power smoothing component in the first tier is unable
to provide sufficient power for the peak in power usage; and reducing
performance of at least one of the one or more devices in response to the
peak in power usage if the first and second power smoothing components
are unable to provide sufficient power for the peak in power usage.

2. A method as recited in claim 1, wherein the first tier comprises one
or more energy storage components that respond to the peak in power usage
by providing power to the one or more devices faster than power smoothing
components in the other tiers of the multiple tiers.

3. A method as recited in claim 1, wherein the first power smoothing
component comprises one or more capacitors.

4. A method as recited in claim 3, wherein each of the one or more
additional power smoothing components comprises one or more batteries of
one or more uninterruptible power supplies.

5. A method as recited in claim 1, the reducing performance of at least
one of the one or more devices comprising sending a signal, to the at
least one of the one or more devices, to throttle its performance.

6. A method as recited in claim 1, wherein the first power smoothing
component in the first tier is unable to provide sufficient power for the
peak in power usage if the first power smoothing component does not hold
enough charge to provide peak power to the one or more devices for the
duration of the peak, the peak power comprising a power usage of the one
or more devices that exceeds a power capacity of a power supply providing
power to the one or more devices.

7. A method as recited in claim 6, wherein the power capacity of the
power supply comprises a maximum power capacity of the power supply.

8. A method as recited in claim 1, wherein the power smoothing component
in the second tier is unable to provide sufficient power for the peak in
power usage if the second power smoothing component does not hold enough
charge to provide peak power to the one or more devices for the duration
of the peak while still meeting a threshold charge level, the peak power
comprising a power usage of the one or more devices that exceeds a
maximum power capacity of a power supply providing power to the one or
more devices.

9. A method as recited in claim 8, wherein the power capacity of the
power supply comprises a maximum power capacity of the power supply.

10. A method as recited in claim 1, further comprising ceasing reducing
performance of the at least one of the one or more devices after the peak
in power usage has passed.

11. A system comprising: a first power smoothing component in one tier of
a hierarchical power smoothing environment having multiple tiers, the
first power smoothing component providing power to one or more devices in
the system in response to a peak in power usage by the one or more
devices; a second power smoothing component in another tier of the
hierarchical power smoothing environment, the second power smoothing
component providing power to the one or more devices in the system in
response to a peak in power usage if the first power smoothing component
does not provide sufficient power for the peak in power usage; and a
third power smoothing component in an additional tier of the hierarchical
power smoothing environment, the third power smoothing component reducing
performance of at least one of the one or more devices if the first power
smoothing component and the second power smoothing component do not
provide sufficient power for the peak in power usage.

12. A system as recited in claim 11, wherein the first power smoothing
component responds to the peak in power usage by providing power to the
one or more devices faster than the second power smoothing component and
the third power smoothing component.

13. A system as recited in claim 11, wherein the first power smoothing
component comprises one or more capacitors in one or more uninterruptible
power supplies.

14. A system as recited in claim 13, wherein the second power smoothing
component comprises one or more batteries of the one or more
uninterruptible power supplies.

15. A system as recited in claim 11, the reducing performance of at least
one of the one or more devices comprising sending a signal, to the at
least one of the one or more devices, to throttle performance of the at
least one of the one or more devices.

16. A system as recited in claim 11, wherein the first power smoothing
component does not provide sufficient power for the peak in power usage
if the first power smoothing component does not hold enough charge to
provide peak power to the one or more devices for the duration of the
peak, the peak power comprising a power usage of the one or more devices
that exceeds a power capacity of a power supply providing power to the
one or more devices.

17. A system as recited in claim 11, wherein the second power smoothing
component does not provide sufficient power for the peak in power usage
if the second power smoothing component does not hold enough charge to
provide peak power to the one or more devices for the duration of the
peak while still meeting a threshold charge level, the peak power
comprising a power usage of the one or more devices that exceeds a
maximum power capacity of a power supply providing power to the one or
more devices.

18. A system as recited in claim 17, wherein the second power smoothing
component comprises one or more batteries of an uninterruptible power
supply, and wherein the threshold charge level comprises an amount of
charge that the one or more batteries are to maintain in order to power
the one or more devices for at least a threshold amount of time in the
event of an interruption in power from an external power source.

19. A system as recited in claim 11, wherein the third power smoothing
component is further to cease reducing performance of the at least one of
the one or more devices after the peak in power usage has passed.

20. A method in a system having a power supply that provides power to one
or more devices and that uses a hierarchical power smoothing environment
having multiple tiers, the method comprising: providing, from a first
power smoothing component in a first tier of the multiple tiers, power to
the one or more devices in response to a peak in power usage by the one
or more devices, the first power smoothing component comprising one or
more capacitors; providing, from a second power smoothing component in a
second tier of the multiple tiers, power to the one or more devices in
response to the peak in power usage if the first power smoothing
component does not provide sufficient power for the peak in power usage,
the second power smoothing component comprising one or more batteries of
an uninterruptible power supply; and reducing performance of at least one
of the one or more devices in response to the peak in power usage if the
first and second power smoothing components are unable to provide
sufficient power for the peak in power usage, wherein the first and
second power smoothing components are unable to provide sufficient power
for the peak in power usage when the one or more capacitors do not hold
enough charge to provide peak power to the one or more devices for the
duration of the peak and the one or more batteries do not hold enough
charge to provide peak power to the one or more devices for the duration
of the peak while still meeting a threshold charge level, wherein the
threshold charge level comprises an amount of charge that the one or more
batteries are to maintain in order to power the one or more devices for
at least a threshold amount of time in the event of an interruption in
power from an external power source.

Description:

BACKGROUND

[0001] Situations arise where it is desirable to have multiple computers
operating together at a particular location to provide a service, such as
data centers or server farms providing services over the Internet. The
computers at those locations, however, do not always consume a constant
amount of power. Rather, the computers oftentimes experience temporary
peaks in their power usage. Having a large enough power supply at these
locations to ensure there is sufficient power for the computers during
such peaks in power usage can be problematic because it can be expensive
to have the power available to provide to the computers during such peaks
even though the peaks are only temporary.

SUMMARY

[0002] This Summary is provided to introduce a selection of concepts in a
simplified form that are further described below in the Detailed
Description. This Summary is not intended to identify key features or
essential features of the claimed subject matter, nor is it intended to
be used to limit the scope of the claimed subject matter.

[0003] In accordance with one or more aspects, a hierarchical power
smoothing environment in a system has multiple tiers and power smoothing
components in each of the multiple tiers. Power is provided to one or
more devices in a system from a first power smoothing component in a
first of the multiple tiers in response to a peak in power usage by the
one or more devices. Additionally, power is provided to the one or more
devices from a second power smoothing component in a second tier of the
multiple tiers if the first power smoothing component is unable to
provide sufficient power for the peak in power usage. If the first and
second power smoothing components are unable to provide sufficient power
for the peak in power usage, then performance of at least one of the one
or more devices is reduced in response to the peak in power usage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The same numbers are used throughout the drawings to reference like
features.

[0005] FIG. 1 illustrates an example system implementing the hierarchical
power smoothing in accordance with one or more embodiments.

[0006]FIG. 2 illustrates an example hierarchical power smoothing
environment including multiple tiers in accordance with one or more
embodiments.

[0007]FIG. 3 illustrates another example hierarchical power smoothing
environment including multiple tiers in accordance with one or more
embodiments.

[0008]FIG. 4 is a flowchart illustrating an example process for
implementing hierarchical power smoothing in accordance with one or more
embodiments.

[0009]FIG. 5 illustrates an example computing device that can be
configured to implement hierarchical power smoothing in accordance with
one or more embodiments.

DETAILED DESCRIPTION

[0010] Hierarchical power smoothing is discussed herein. In a system
including one or more devices, multiple power smoothing components are
implemented at different hierarchical tiers. In the event of a peak in
power usage by the one or more devices, the power smoothing components at
one or more tiers attempt to provide sufficient power for the peak in
power usage. Different types of power smoothing components are used at
different tiers, with the power smoothing components at lower tiers
typically responding faster (and typically providing power for shorter
durations) than components at higher tiers. At a highest tier, if power
smoothing components at the lower tiers are not able to provide
sufficient power for the peak in power usage, then performance of the one
or more devices is reduced (e.g., devices are throttled).

[0011] FIG. 1 illustrates an example system 100 implementing the
hierarchical power smoothing in accordance with one or more embodiments.
System 100 includes a server system 102 that operates to provide one or
more services to various computing devices. These computing devices can
be located in close physical proximity to server system 102, and/or
located across a wide geographic range (e.g., throughout a country or
throughout the world). Server system 102 can communicate with such
computing devices via a variety of different networks, including the
Internet, a local area network (LAN), a cellular or other phone network,
an intranet, other public and/or proprietary networks, combinations
thereof, and so forth. Server system 102 can be accessed by a variety of
different types of computing devices, such as a desktop computer, a
laptop or netbook computer, a tablet or notepad computer, a mobile
station, an entertainment appliance, a television, a set-top box
communicatively coupled to a display device, a cellular or other wireless
phone, a game console, an automotive computer, and so forth.

[0012] Server system 102 can provide one or more of a variety of different
services to computing devices. For example, server system 102 can provide
one or more of a social networking service, an email service, a search
service, an information resource/storage service, a messaging service, an
image and/or video sharing service, a gaming or other entertainment
service, and so forth. The one or more services provided by server system
102 can be publicly available or alternatively access to one or more of
the services can be restricted to particular users (e.g., those having a
valid account as verified by a service of server system 102).

[0013] Server system 102 includes multiple (m) devices 104(1), . . . ,
104(m) that operate to provide the functionality of the one or more
services provided by server system 102. Devices 104 typically include one
or more server computers, such as rack servers or blade servers, and
system 102 is thus also referred to as a server system. Alternatively, a
variety of other types of devices or components can be included as
devices 104, such as other types of computing devices, networking
components (e.g., a gateway, a router, a switch, etc.), data storage
components (e.g., one or more magnetic disk drives), cooling components
(e.g., a fan), and so forth.

[0014] In one or more embodiments, devices 104 are located within racks of
server system 102. A rack is a physical structure or housing into which
multiple chassis can be inserted, mounted, or otherwise placed.
Alternatively, devices 104 can be grouped into other containers, mounting
units, or other grouping configurations. For example, devices 104 can be
housed independently (e.g., not within a rack) and communicate with one
another via a network or other communication link. Server system 102 can
thus range from, for example, a large data center or server farm
including thousands of servers housed in numerous racks providing
services over the Internet, to a few server computers in their own
individual housings providing services over a LAN to a small company.

[0015] Server system 102 receives external power 106. External power 106
can be received from one or more conventional external power sources,
such as a power station managed by a power utility company. External
power 106 can also be received from a backup power generator that
operates as a backup source of power in the event of an interruption in
power from another source (such as a power utility company). Such a
backup generator can be, for example, a diesel-powered or gas-powered
generator, a fuel cell based generator, and so forth. External power 106
can be AC power that is converted to DC power by server system 102 and/or
can be DC power (that may or may not be converted to different voltage
levels by server system 102).

[0016] Situations can also arise where there is a peak in power usage of
one or more devices 104. A peak in power usage refers to the situation
where the amount of power being consumed by one or more devices meets
(e.g., is equal to or greater than) a threshold amount. This threshold
amount can be set by, for example, a designer or administrator of server
system 102. This threshold amount can be based on, for example, an
average amount of power the one or more devices consume (e.g., averaged
over some period of time, such as minutes, hours, days, etc.).

[0017] Server system 102 includes hierarchical power smoothing components
110. Hierarchical power smoothing components 110 include multiple
components that operate to provide power to one or more devices 104
during peaks in power usage. This power is in addition to external power
106. Hierarchical power smoothing components 110 include components at
multiple different tiers, as discussed in more detail below.

[0018] Hierarchical power smoothing components 110 include one or more
uninterruptible power supplies (UPS's) 112, one or more other energy
storage components 114, and one or more performance reduction components
116. Alternatively, other power smoothing components can be included in
components 110 in addition to and/or in place of one or more of a UPS
112, energy storage component 114, and performance reduction component
116.

[0019] Each UPS 112 includes one or more batteries, and thus is also an
energy storage component. These batteries can be a variety of different
types of batteries, such as sealed lead-acid batteries, lithium ion
batteries, and so forth. Energy storage components 114 are other types of
energy storage components other than batteries of a UPS, such as one or
more capacitors. Energy storage components 114 can also generate energy,
such as one or more backup generators. Performance reduction components
116 reduce the performance of one or more devices 104, such as by using
throttling. Throttling reduces the performance of a device 104 and thus
at the same time reduces power consumption of the device 104. Performance
reduction component 116 sends a signal or request to one or more of the
devices 104 indicating that the one or more devices are to throttle their
performance. These devices are configured in different manners to reduce
or throttle their performance, such as by reducing power to a component
(e.g., a processor), shutting down a component (e.g., shutting down one
of multiple processor cores), slowing down operation of a component
(e.g., reducing the clock speed of a processor or the rotational speed of
a disk drive), and so forth.

[0020] One or more of hierarchical power smoothing components 110 can also
be used for other operations within server system 102 in addition to
power smoothing. For example, UPS 112 detects interruptions in external
power 106 and provides power (DC power or AC power) to devices 104 if
there is an interruption in external power 106. UPS 112 can, for example,
provide power to devices 104 during a time period between the
interruption in power from another source (such as a power utility
company) and a backup generator generating sufficient AC power to power
server system 102. UPS 112 can also provide power to devices 104 in
situations where there is no backup generator for server system 102. By
way of another example, performance reduction components 116 can be used
to reduce the performance of one or more devices 104 in response to other
events, such as in response to a desire to reduce power consumption in
system 102.

[0021] Different ones of hierarchical power smoothing components 110 can
also be physically located in different areas of server system 102. For
example, a UPS 112 can be a single full server system UPS in its own
housing that is located in a same room (or same building) as devices 104
and that provides power to all devices in server system 102, to multiple
device level UPS's that are each located within a device 104 and each
provide power to a single device 104. UPS's 112 can also be located in
multiple areas, such as a server system level UPS in a separate room from
devices 104 that provides power to multiple racks of devices 104, a rack
level UPS that is included in the same rack as some devices 104 and
provides power to devices 104 in that same rack, a device level UPS that
is included in a device 104 and provides power to that device 104,
combinations thereof, and so forth. By way of another example, energy
storage components 114 (such as capacitors) can be included in a
particular rack with some devices 104, can be included within devices
104, and so forth.

[0022] Additionally, although illustrated as being part of server system
102, one or more hierarchical power smoothing components 110 can be
implemented external to server system 102. For example, a UPS 112 can be
implemented external to server system 102, a power generator can be
implemented external to server system 102, and so forth.

[0023] In one or more embodiments, the different energy storage components
(UPS 112 and other energy storage component 114) are configured to
respond to peaks in power usage by providing power to one or more devices
104 during peaks in power usage. Different technologies are used to
implement the different types of components, and these different
technologies respond (by providing power during a peak in power usage) at
different rates. Components at lower tiers of the hierarchical power
smoothing components 110 respond faster (but typically provide power for
shorter durations) than components at higher tiers of the hierarchical
power smoothing components 110. For example, components at a lowest tier
of hierarchical power smoothing components 110 can be capacitors that
respond very quickly to a peak in power usage, while a higher tier of
hierarchical power smoothing components 110 can be batteries that respond
more slowly to the peak in power usage.

[0024] The physical location of particular hierarchical power smoothing
components 110 in server system 102 varies based at least in part on the
particular types of components 110 and the particular technology used to
implement those different types of components 110. Components that are
physically located closer to devices 104 in system 102 are components
that can respond to and provide power during peaks in power usage faster
than components that are physically located further from devices 104.
These faster responding components also typically (but not necessarily)
are able to provide power during peaks for shorter durations than
components that are slower in responding to and providing power during
peaks in power usage.

[0025] Additionally, it should be noted that the discussions herein refer
to peaks in power usage, which can also be referred to as spikes up in
power. The hierarchical power smoothing discussed herein can analogously
be used to provide power during a spike down in power or power loss.
Thus, a spike down in power or power loss can analogously be detected,
and power can be provided by hierarchical power smoothing components 110
during the spike down in power or power loss analogously to providing
power during a spike up in power.

[0026] A spike down in power or power loss can also be detected in a
higher tier of hierarchical power smoothing components, and an indication
of the spike down in power or power loss can be communicated to lower
tiers of the hierarchical power smoothing components. This can result in
reducing the ability of one or more components of the hierarchical power
smoothing components to provide sufficient power for a peak in power
usage as discussed below (e.g., the spike down in power or power loss can
lead to peaks in power usage that are larger and/or longer in duration).

[0027]FIG. 2 illustrates an example hierarchical power smoothing
environment 200 including multiple tiers in accordance with one or more
embodiments. Hierarchical power smoothing environment 200 is implemented
using, for example, hierarchical power smoothing components 110 of FIG.
1. Hierarchical power smoothing environment 200 can be implemented in
software, firmware, hardware, or combinations thereof. Hierarchical power
smoothing environment 200 is an example, and other environments can use
different components.

[0028] Hierarchical power smoothing environment 200 provides power to
particular devices during peaks in power usage. Accordingly, different
hierarchical power smoothing environments 200 can be used for different
sets of devices in a server system (e.g., in server system 102 of FIG.
1).

[0029] Hierarchical power smoothing environment 200 includes four tiers
202(1), 202(2), 202(3), and 202(4). Tiers 202 are ordered in the
hierarchy from a lowest tier (tier 202(1)) to a highest tier (tier
202(4)). Each tier 202 includes a different type of power smoothing
component.

[0030] In the lowest tier, tier 202(1), one or more capacitors 210 are
included as energy storage components. These capacitors 210 are located
physically close to the devices to which hierarchical power smoothing
environment 200 provides power. For example, capacitors 210 can be
located in the devices to which hierarchical power smoothing environment
200 provides power, or in the same racks as the devices to which
hierarchical power smoothing environment 200 provides power. Capacitors
210 respond quickly to peaks in power usage, providing power to the
devices during such peaks in power usage faster than components in higher
tiers (tiers 202(2), 202(3), and 202(4)).

[0031] In the next higher tier, tier 202(2), one or more batteries 212 of
a UPS are included as energy storage components. These batteries 212 are
typically located physically close to the devices to which hierarchical
power smoothing environment 200 provides power, but may not be as close
as capacitors 210. Batteries 212 can be, for example, in the devices to
which hierarchical power smoothing environment 200 provides power, in the
same rack as the devices to which hierarchical power smoothing
environment 200 provides power, or alternatively elsewhere in the server
system. Batteries 212 are slower in responding to peaks in power usage
than capacitors 210, but also typically are able to provide power for
longer peaks in power usage than capacitors 210 can provide power.
Batteries 212 are also able to respond to peaks in power usage, providing
power to the devices during such peaks in power usage faster than
components in higher tiers (tiers 202(3) and 202(4)).

[0032] In the next higher tier, tier 202(3), a generator 214 is included
as an energy storage component. Generator 214 is typically physically
located further from the devices than capacitors 210 and batteries 212.
For example, generator 214 may be located in a different room of the same
building as the devices to which hierarchical power smoothing environment
200 provides power, or in a different building. Generator 214 is slower
in responding to peaks in power usage than capacitors 210 and batteries
212, but is also typically able to provide power for longer peaks in
power usage than capacitors 210 or batteries 212 can provide power.

[0033] In the highest tier, tier 202(4), device throttling 216 is included
as a power smoothing component. In tier 202(4), a signal or request is
sent to one or more of the devices indicating that the one or more
devices are to throttle their performance, thereby reducing the power
usage of such devices. Device throttling 216 is the highest tier, and
thus is used after the energy storage components in the lower tiers
(tiers 202(1), 202(2), and 202(3)) are no longer able to provide
sufficient power for a peak in power usage. Energy storage components in
the lower tiers may be no longer able to provide sufficient power for a
peak in power usage because, for example, the charge in the energy
storage components has been depleted, the peak is greater than an amount
of power that the energy storage components can provide, and so forth.
Device throttling 216 can be used indefinitely.

[0034] In the example of FIG. 2, capacitor energy storage 210, battery
energy storage 212, and generator energy storage 214 are illustrated.
More generally, capacitor energy storage 210 can be any of a variety of
energy storage components that provide a very small amount of energy for
a very short amount of time (e.g., less than 200 Watts for less than one
second), battery energy storage 212 can be any of a variety of energy
storage components that provide a small amount of energy for a small
amount of time (e.g., less than 200 Megawatts for less than 10 minutes),
and generator energy storage 214 can be any of a variety of energy
storage components that provide a large amount of energy for a large
amount of time (e.g., less than 30 Megawatts for a number of days (e.g.,
as long as there is fuel for the generator)). Battery energy storage 212
provides more energy and/or energy for a longer amount of time than
capacitor energy storage 210, and generator energy storage 214 provides
more energy and/or energy for a longer amount of time than battery energy
storage 212.

[0035] Thus, in hierarchical power smoothing environment 200, fast
responding power smoothing components are located at lower tiers and
physically closer to the devices to which hierarchical power smoothing
environment 200 provides power. The fast responding power smoothing
components are thus able to quickly provide power to devices in the event
of a peak in power usage. Slower responding power smoothing components
are located at higher tiers and physically further from the devices to
which hierarchical power smoothing environment 200 provides power.
However, such slower responding power smoothing components can typically
provide power for longer peaks in power usage than the faster responding
power smoothing components. The slower responding power smoothing
components are thus able to provide power for a longer duration in the
event of a peak in power usage (e.g., continuing to provide power for the
peak in power usage after the charge in power smoothing components of
lower tiers has been depleted).

[0036]FIG. 3 illustrates another example hierarchical power smoothing
environment 300 including multiple tiers in accordance with one or more
embodiments. Hierarchical power smoothing environment 300 is implemented
using, for example, hierarchical power smoothing components 110 of FIG.
1. Hierarchical power smoothing environment 300 can be implemented in
software, firmware, hardware, or combinations thereof. Hierarchical power
smoothing environment 300 is a general example of a hierarchical power
smoothing environment, and environment 300 can be hierarchical power
smoothing environment 200 of FIG. 2.

[0037] Hierarchical power smoothing environment 300 includes multiple (n)
tiers 302(1), 302(2), . . . , 302(n). Tiers 302 are ordered in the
hierarchy from a lowest tier (tier 302(1)) to a highest tier (tier
302(n)). For example, tier 302(2) is a next higher tier from tier 302(1),
and tier 302(n-1) is a next lower tier from tier 302(n).

[0038] Each tier 302 includes a power smoothing component 304 and a peak
detection component 306. Alternatively, the same one or more peak
detection components 306 can be used by multiple tiers 302. The power
smoothing components 304 at different tiers 302 are typically different
types of power smoothing components. Different technologies are used to
implement the different types of components in the different tiers 302.
As discussed above, these different technologies are configured to
respond to (provide peak power during) peaks in power usage. Power
smoothing components at a lower tier of hierarchical power smoothing
environment 300 respond faster (but typically provide power for shorter
durations) than components at higher tiers of hierarchical power
smoothing environment. For example, components at a tier 302(x), where
x≦n, typically respond faster but provide power for a shorter
duration than components at tier 302(x+1), and respond slower but provide
power for a longer duration than components at tier 302(x-1).

[0039] The number of tiers 302, as well as the particular types of
components in the different tiers 302, is selected by an administrator
and/or customers of the server system implementing hierarchical power
smoothing environment 300 to provide the power smoothing desired by the
administrator and/or customers. Additionally, the time taken by a power
smoothing component 304 in one tier to respond to a peak in power usage
can be used by the administrator and/or customers as a basis for
determining a number and/or capacity of power smoothing components 304 to
employ in a next lower tier. For example, a number and/or capacity of
capacitors to be used in tier 302(1) can be selected based on an amount
of time taken by batteries in tier 302(2) to respond to a peak in power
usage, so that the capacitors in tier 302(1) provide sufficient power for
the peak in power usage until the batteries in tier 302(2) are able to
provide power for the peak in power usage.

[0040] In each tier 302, a peak in power usage by one or more devices in
the server system employing hierarchical power smoothing environment 300
(e.g., server system 102 of FIG. 1) is detected by the peak detection
component 306 in that tier. A peak detection component 306 can detect a
peak in power usage in a variety of different manners. In one or more
embodiments, devices in the server system are powered by one or more
power supplies. Each power supply can provide power to one or more
devices (e.g., to a single device, to the devices in a rack or other
collection of devices, and so forth). A peak in power usage is detected
by monitoring one or more of various indicators related to a power supply
associated with the one or more devices to determine when peak power
usage meets (e.g., equals or exceeds) a threshold value. This threshold
value can be, for example, a maximum power capacity of the power supply,
a value set at some point below the maximum power capacity of the power
supply (e.g., 90% of the maximum power capacity of the power supply), and
so forth. If the threshold current power usage by the one or more devices
powered by the power supply meets (e.g., equals or exceeds) the threshold
value, then the presence of a peak in power usage is detected.

[0041] One or more of a variety of indicators can be used to identify the
power usage of devices receiving power from the power supply. For
example, the input current of AC power to a power supply can be
monitored, such as by using a series resistor or inductive loop. By way
of another example, the output current of a power supply can be
monitored, such as by using a series resistor, inductive loop, or
monitoring the voltage drop across an output FET (field-effect
transistor). By way of yet another example, the switching frequency of an
output rectifier of the power supply can be monitored.

[0042] In a server system, one or more power supplies provide power to the
devices in the server system, and different server systems can be
configured with power supplies in different locations. For example, a
particular server system may have a backup generator that provides power
to all racks of the server system, and each rack can have one or more
power supplies that provide power to one or more devices in that rack. By
way of another example, a particular server system may have a backup
generator that provides power to all racks of the server system, and each
device in each rack can have a power supply that provides power to that
device.

[0043] Each tier 302 is typically associated with a particular power
supply of the server system. A peak in power usage detected by peak
detection components 306 in a particular tier 302 is a peak in power
usage for the one or more devices that are powered by a particular power
supply associated with that tier. In response to a detected peak in power
usage, power smoothing component 304 provides power for the peak in power
usage to the devices powered by the power supply associated with that
tier. For example, tier 302(1) may be associated with a particular rack
of the server system and peak detection component 306(1) detects peaks in
power usage by the devices (collectively) in that particular rack. In
response to a detected peak in power usage, power smoothing component
304(1) provides power to the devices in that particular rack. By way of
another example, tier 302(2) may be associated with a backup generator
that provides power to multiple racks of the server system and peak
detection component 306(2) detects peaks in power usage by the multiple
racks (collectively) in the server system. In response to a detected peak
in power usage, power smoothing component 304(2) provides power to the
devices in those multiple racks.

[0044] In response to a peak in power usage being detected by a peak
detection component 306 in a particular tier 302, a power smoothing
component 304 in that particular tier 302 attempts to provide sufficient
power for the peak in power usage. Peak detection component 306 can send
a command or signal to the power smoothing component 304 in that
particular tier 302 to provide power during the peak, or the power
smoothing component 304 can be otherwise configured to automatically
provide power during a peak. If the power smoothing component 304 in that
particular tier is successful in providing sufficient power for the peak
in power usage, then power smoothing components from other tiers 302 need
not provide power for the peak in power usage.

[0045] However, if the power smoothing component in a particular tier 302
is unable to provide sufficient power for the peak in power usage, then
the power smoothing component 304 in that tier (the next higher tier in
which the peak in power usage is detected) attempts to provide sufficient
power for the peak in power usage. This power can be in addition to or
alternatively in place of the power provided by the lower tier.

[0046] Whether the power smoothing component in a particular tier is able
to provide sufficient power for a peak in power usage can be determined
or identified in a variety of different manners. In one or more
embodiments, a power smoothing component holds a particular amount of
charge or energy. Whether the power smoothing component can provide
sufficient power for a peak in power usage is determined based on whether
the power smoothing component holds enough charge to provide the peak
power to the one or more devices for the duration of the peak. The peak
power refers to the power usage of the one or more devices that exceeds a
particular power capacity of the power supply providing power to the one
or more devices. This particular power capacity can be a maximum power
capacity of the power supply, or alternatively another value (e.g., a
fraction of the maximum power capacity (e.g., 90% of the maximum power
capacity), an amount that is the threshold amount used for determining
whether there is a peak in power usage as discussed above, etc.).

[0047] Alternatively, whether the power smoothing component can provide
sufficient power for a peak in power usage can be determined based on
whether the power smoothing component holds enough charge to provide the
peak power to the one or more devices for the duration of the peak while
still meeting (e.g., staying at or above) a threshold charge level. This
threshold charge level can be, for example, an amount of charge that
batteries of a UPS are to maintain in order to power the one or more
devices for at least a threshold amount of time in the event of an
interruption in power from an external power source (e.g., external power
106 of FIG. 1).

[0048] In one or more embodiments, power smoothing components 304 and peak
detection components 306 in different tiers 302 operate to provide power
during a peak in power usage independently of one another. At each tier
302, when the peak detection component 306 detects a peak in power usage,
the power smoothing component 304 in that tier responds by providing
power for the peak in power usage. With different types of components
being used in different tiers as discussed above, this results in the
power detection components 306 of multiple tiers detecting the peak in
power usage and the power smoothing components 304 in each of those
multiple tiers responding to the detection by providing power for the
peak in power usage. However, as the different types of components at the
different tiers have different response times, lower tiers 302 will
provide power for the peak in power usage more quickly than higher tiers.

[0049] Alternatively, in one or more embodiments peak detection components
306 can communicate various information or data regarding peaks in power
usage with one another. This information or data can include information
identifying that a peak in power usage has been detected by a particular
peak detection component 306. For example, peak detection component
306(1) can provide an indication to peak detection component 306(2) that
component 306(1) has detected a peak in power usage, and this indication
can be passed up to the peak detection components 306 at the higher
tiers.

[0050] This information or data communicated between peak detection
components can also include information identifying whether to respond to
a peak in power usage. For example, peak detection component 306(n) can
provide an indication to peak detection component 306(n-1) to no longer
provide power during a peak in power usage because peak detection
component 306(n) is now able to provide power for the peak in power
usage.

[0051] It should also be noted that less than all power smoothing
components 304 may provide power during a particular peak in power usage.
For example, if a particular peak in power usage is very short and power
smoothing component 304(1) has sufficient capacity to provide power for
the peak in power usage, then other power smoothing components (e.g.,
power smoothing components 304(2) . . . 304(n)) need not provide power
during that peak in power usage. Such other power smoothing components
may begin to respond to the peak in power usage, but the peak is over
before such other power smoothing components are able to provide power.

[0052] The power smoothing component 304(n) in the highest tier in
hierarchical power smoothing environment 300 (tier 302(n)) reduces the
performance of one or more devices. Power smoothing component 304(n)
reduces the performance of the one or more devices by, for example,
throttling the devices as discussed above. The one or more devices for
which performance is reduced is the one or more devices powered by the
particular power supply associated with the highest tier (tier 302(n)).
For example, if the power supply associated with the highest tier is a
backup generator for the server system, then the performance of one or
more devices in the server system is reduced. By way of another example,
if the power supply associated with the highest tier is a power supply
for a particular rack in the server system, then the performance of one
or more devices in that particular rack is reduced.

[0053] The power smoothing component 304(n) can reduce the performance of
all devices that receive power from the particular power supply
associated with the highest tier, or alternatively from one or more
select devices (e.g., one or more devices that have the highest peak in
power usage, one or more devices that are identified as lower priority
devices, and so forth). Additionally, power smoothing component 304(n)
can reduce the performance of a particular one or more devices that
receive power from the particular power supply associated with the
highest tier, while other devices that receive power from the particular
power supply associated with the highest tier continue to receive power
for the peak in power usage from energy storage components in lower tiers
(e.g., one or more power smoothing components in a tier below tier
304(n)).

[0054] After a peak in power usage has passed, any power smoothing
components 304 that are providing power to the one or more devices cease
providing such power. Similarly, any reduction in the performance of the
one or more devices is also ceased (e.g., a signal or request is sent to
the one or more devices to inform the one or more devices that they no
longer need to throttle their performance). The peak detection components
306 detect when there is no longer a peak in power usage, and thus when
the power smoothing components 304 can cease providing power to the one
or more devices. This ceasing of providing power and reducing performance
can be done in accordance with the ordering of the tiers (from highest to
lowest tier). For example, as the peak in power usage passes (or the peak
declines), any reduction in the performance of the one or more devices is
ceased. Then any power supplied by the next lowest tier ceases being
supplied, then power supplied by the next lowest tier ceases being
supplied, and so forth.

[0055] Additionally, after a peak in power usage has passed one or more
components that were used to provide power to the one or more devices
during the peak in power usage can be recharged. For example, batteries
are recharged, capacitors are recharged, and so forth. Additionally, if
there is sufficient power available from a power supply, one or more
components can be recharged prior to the peak in power usage completely
passing.

[0056] Although hierarchical power smoothing environment 300 is
illustrated as having a separate peak detection component 304 in each
tier, alternatively, a single peak detection component 304 can correspond
to and be used for multiple (e.g., all) tiers 302 in hierarchical power
smoothing environment 300. In such embodiments, the single peak detection
component 304 detects peaks in power usage and invokes the power
smoothing components of the corresponding multiple tiers 302 to attempt
to provide sufficient power for the peak in power usage.

[0057] Thus, different energy storage components at different tiers are
used to provide power during peaks in power usage. Different technologies
are used to implement the different types of energy storage components in
the different tiers, with energy storage components at lower tiers
responding faster (but typically providing power for shorter durations)
than energy storage components at higher tiers. If the energy storage
components are not able to provide sufficient power for the peak in power
usage, then the performance of the devices is reduced (e.g., using
throttling).

[0058]FIG. 4 is a flowchart illustrating an example process 400 for
implementing hierarchical power smoothing in accordance with one or more
embodiments. Process 400 can be implemented in software, firmware,
hardware, or combinations thereof. Process 400 is shown as a set of acts
and is not limited to the order shown for performing the operations of
the various acts. Process 400 is an example process for implementing
hierarchical power smoothing; additional discussions of implementing
hierarchical power smoothing are included herein with reference to
different figures.

[0059] In process 400, power usage by one or more devices is monitored
(act 402). These one or more devices can be the devices that are powered
by a particular power supply as discussed above. This monitoring can be
monitoring of one or more of various indicators related to a power supply
as discussed above.

[0060] Process 400 proceeds based on whether a peak in power usage by the
one or more devices is detected (act 404). If no peak in power usage is
detected, then process returns to act 402 where monitoring of the power
usage by the one or more devices continues.

[0061] However, if a peak in power usage by the one or more devices is
detected, then power is provided to the one or more devices from one or
more energy storage components in a hierarchical power smoothing
environment (act 406). These energy storage components can include
different types of energy storage components (e.g., capacitors,
batteries, generators, etc.) in different tiers as discussed above.

[0062] Process 400 proceeds based on whether the power provided by energy
storage components from act 406 is sufficient power for the peak in power
usage (act 408). Whether the power provided by these energy storage
components is sufficient power for a peak in power usage can be
determined or identified in a variety of different manners as discussed
above.

[0063] If the power provided by the energy storage components from act 406
is not sufficient power for the peak in power usage, then the performance
of at least one of the one or more devices is reduced (act 410). The
performance of at least one device can be reduced by, for example,
throttling the performance of the at least one device. Process 400 then
returns to act 402 where monitoring of the power usage by the one or more
devices continues.

[0064] Returning to act 408, if the power provided by the energy storage
devices from act 406 is sufficient power for the peak in power usage,
then process 400 proceeds based on whether performance of at least one
device was previously reduced (act 412). The performance of at least one
device can have been previously reduced in act 410 discussed above.

[0065] If the performance of at least one device was not previously
reduced, then process 400 then returns to act 402 where monitoring of the
power usage by the one or more devices continues. However, if the
performance of at least one device was previously reduced, then reducing
the performance of the at least one device is ceased (act 414). Process
400 then returns to act 402 where monitoring of the power usage by the
one or more devices continues.

[0066] Thus, it can be seen that the hierarchical power smoothing
techniques discussed herein allow peaks in power usage to be powered by
multiple different energy storage components before performance of the
one or more devices is reduced. For example, power for short peaks can be
provided by capacitors, power for longer peaks can be provided by UPS
batteries, and for even longer peaks the performance of the one or more
devices is throttled. This allows the one or more devices to be powered
by multiple energy storage components before needing to reduce their
performance and allows them to keep running at their full or desired
performance level for a longer amount of time. Additionally, the one or
more devices are allowed to keep running without reducing their
performance and without requiring a large amount of extra power capacity
to be available in the system solely to provide power during such peaks
in power usage.

[0067] Additionally, returning to FIG. 1, the particular hierarchical
power smoothing components 110 that are included in server system 102 can
vary based on the desires of the administrator and/or customers of server
system 102. Different customers can select different hierarchical power
smoothing components 110, thus incurring the cost for only the power
smoothing capability they desire to have. For example, a first set of
devices 104 can be owned or leased by a first company (or business unit),
while a second set of devices can be owned or leased by a second company
(or business unit). The first company may desire to include capacitors,
UPS's, and device throttling in hierarchical power smoothing components
110. The second company, however, may desire to include only device
throttling in hierarchical power smoothing components 110. Thus, the
first company incurs the cost of purchasing and maintaining capacitors,
UPS's, and device throttling components, while the second company incurs
only the cost of purchasing and maintaining device throttling components.

[0068]FIG. 5 illustrates an example computing device 500 that can be
configured to implement hierarchical power smoothing in accordance with
one or more embodiments. Computing device 500 can be, for example, a
device or controller for UPS 112 of FIG. 1, or a device or controller
implementing hierarchical power smoothing environment 200 of FIG. 2 or
hierarchical power smoothing environment 300 of FIG. 3. Computing device
500 can also be a device 104 of FIG. 1.

[0069] Computing device 500 includes one or more processors or processing
units 502, one or more computer readable media 504 which can include one
or more memory and/or storage components 506, one or more input/output
(I/O) devices 508, and a bus 510 that allows the various components and
devices to communicate with one another. Computer readable media 504
and/or one or more I/O devices 508 can be included as part of, or
alternatively may be coupled to, computing device 500. Bus 510 represents
one or more of several types of bus structures, including a memory bus or
memory controller, a peripheral bus, an accelerated graphics port, a
processor or local bus, and so forth using a variety of different bus
architectures. Bus 510 can include wired and/or wireless buses.

[0071] The techniques discussed herein can be implemented in software,
with instructions being executed by one or more processing units 502. It
is to be appreciated that different instructions can be stored in
different components of computing device 500, such as in a processing
unit 502, in various cache memories of a processing unit 502, in other
cache memories of device 500 (not shown), on other computer readable
media, and so forth. Additionally, it is to be appreciated that the
location where instructions are stored in computing device 500 can change
over time.

[0072] One or more input/output devices 508 allow a user to enter commands
and information to computing device 500, and also allows information to
be presented to the user and/or other components or devices. Examples of
input devices include a keyboard, a cursor control device (e.g., a
mouse), a microphone, a scanner, and so forth. Examples of output devices
include a display device (e.g., a monitor or projector), speakers, a
printer, a network card, and so forth.

[0073] Various techniques may be described herein in the general context
of software or program modules. Generally, software includes routines,
programs, objects, components, data structures, and so forth that perform
particular tasks or implement particular abstract data types. An
implementation of these modules and techniques may be stored on or
transmitted across some form of computer readable media. Computer
readable media can be any available medium or media that can be accessed
by a computing device. By way of example, and not limitation, computer
readable media may comprise "computer storage media" and "communications
media."

[0074] "Computer storage media" include volatile and non-volatile,
removable and non-removable media implemented in any method or technology
for storage of information such as computer readable instructions, data
structures, program modules, or other data. Computer storage media
include, but are not limited to, RAM, ROM, EEPROM, flash memory or other
memory technology, CD-ROM, digital versatile disks (DVD) or other optical
storage, magnetic cassettes, magnetic tape, magnetic disk storage or
other magnetic storage devices, or any other medium which can be used to
store the desired information and which can be accessed by a computer.

[0075] "Communication media" typically embody computer readable
instructions, data structures, program modules, or other data in a
modulated data signal, such as carrier wave or other transport mechanism.
Communication media also include any information delivery media. The term
"modulated data signal" means a signal that has one or more of its
characteristics set or changed in such a manner as to encode information
in the signal. By way of example, and not limitation, communication media
include wired media such as a wired network or direct-wired connection,
and wireless media such as acoustic, RF, infrared, and other wireless
media. Combinations of any of the above are also included within the
scope of computer readable media.

[0076] Generally, any of the functions or techniques described herein can
be implemented using software, firmware, hardware (e.g., fixed logic
circuitry), manual processing, or a combination of these implementations.
The terms "module" and "component" as used herein generally represent
software, firmware, hardware, or combinations thereof. In the case of a
software implementation, the module or component represents program code
that performs specified tasks when executed on a processor (e.g., CPU or
CPUs). The program code can be stored in one or more computer readable
memory devices, further description of which may be found with reference
to FIG. 5. The features of the hierarchical power smoothing described
herein are platform-independent, meaning that the techniques can be
implemented on a variety of commercial computing platforms having a
variety of processors.

[0077] Although the subject matter has been described in language specific
to structural features and/or methodological acts, it is to be understood
that the subject matter defined in the appended claims is not necessarily
limited to the specific features or acts described above. Rather, the
specific features and acts described above are disclosed as example forms
of implementing the claims.